1,3,5-Triazacyclohexane 2,6-diaminopurine Biology, life sciences C–H···π interaction C–I···F halogen bonds DFT study EDTA H-bonding Hirshfeld surface analysis Lewis acids Lewis bases PBE0-D3(BJ) calculations Research & information: general Schiff bases cadmium chalcogen bonding characterizations co-crystal coinage metals crystal engineering crystal growth crystallography direct measure for π–hole interaction strength halogen bonding hybridization of a nitrogen atom in sulfonamides hydrogen bonding hydrogen bonding sigma-hole interactions local vibrational mode theory main group elements molecular cocrystal